Vehicles that have higher gross vehicle weights (GVW) are specifically designed to carry and tow amounts of weight that may not be typically associated with passenger vehicles. Such vehicles may be used for construction, recreation, and commercial purposes. Even though these vehicles may sometimes operate at weights that are far below the GVW, the vehicles are designed to deliver adequate part accelerator pedal performance in both laden and un-laden conditions. Further, the vehicles may be required to meet performance metrics at the GVW so that the customer receives a vehicle that performs well at the GVW. However, a vehicle that is operating at its GVW may perform significantly different than a vehicle that is operating at its base vehicle weight. For example, the vehicle may accelerate better at its base weight as compared to when operating at its GVW. Additionally, the improved vehicle acceleration may come at the expense of decreased fuel economy.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating an engine of a vehicle, comprising: providing a driver input device for determining a driver demand torque; transforming a signal from the driver input device into a driver demand torque via a transfer function that is based on operating the vehicle at a gross vehicle weight; and adapting the transfer function in response to vehicle weight being less than a gross vehicle weight.
By adapting a transfer function that influences driver demand torque in response to vehicle weight being less than a gross vehicle weight, it may be possible to provide more consistent vehicle performance over a wider range of vehicle weights. Further, it may be possible to provide improved fuel economy at higher driver demands when the vehicle is operated at a lower weight. For example, a driver demand transfer function may be based on performance objectives and emissions for operating a vehicle at its GVW. If the vehicle is operated at less than its GVW, the driver demand transfer function may be adapted to provide the same level of vehicle performance (e.g., acceleration) at the reduced vehicle weight. Maintaining the same level of vehicle performance at the lower vehicle weight as at the higher vehicle weight may allow higher fuel efficiency to be achieved at lower vehicle weights. Additionally, the vehicle may perform more consistently over a wider range of vehicle weights so that the driver may expect a certain level of performance irrespective of vehicle weight.
The present description may provide several advantages. In particular, the approach may improve vehicle fuel economy when a vehicle is operated at lower vehicle loads. Further, the approach may provide a more consistent level of vehicle performance even in the presence of varying vehicle loads. Further still, the approach may reduce wear of driveline components such as transmission clutches since the vehicle may operate with less variation.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.